### Abstract

- Top of page
- Abstract
- Introduction
- Correlation
- Agreement
- Box 1: Worked example of Pearson, ICC and limits of agreement
- Precision (repeatability and reproducibility)
- Relationship between the average and the difference in agreement studies
- Sample size for agreement studies
- One eye or two?
- Summary
- Acknowledgements
- Bibliography
- References
- Appendices

**Citation information**: McAlinden C, Khadka J & Pesudovs K. Statistical methods for conducting agreement (comparison of clinical tests) and precision (repeatability or reproducibility) studies in optometry and ophthalmology. *Ophthalmic Physiol Opt* 2011, **31**, 330–338. doi: 10.1111/j.1475-1313.2011.00851.x

#### Abstract

The ever-expanding choice of ocular metrology and imaging equipment has driven research into the validity of their measurements. Consequently, studies of the agreement between two instruments or clinical tests have proliferated in the ophthalmic literature. It is important that researchers apply the appropriate statistical tests in agreement studies. Correlation coefficients are hazardous and should be avoided. The ‘limits of agreement’ method originally proposed by Altman and Bland in 1983 is the statistical procedure of choice. Its step-by-step use and practical considerations in relation to optometry and ophthalmology are detailed in addition to sample size considerations and statistical approaches to precision (repeatability or reproducibility) estimates.